The synthesis and characterisation of carbohydrate-functionalised porphyrazines

A synthetic pathway to the incorporation of mono- and disaccharide carbohydrate moieties into porphyrazine systems was demonstrated. A range of selectively protected monosaccharide precursors was coupled to a small variety of phthalonitriles; the intermediates were co-macrocyclised to form hybrid porphyrazines in Linstead macrocyclisation reactions. Demetallisation of Mg-porphyrazine products was readily effected to afford the free-base pigments, which were subsequently converted into their zinc or nickel complexes. Some porphyrazines were deprotected of their isopropylidene groups (on the carbohydrate moieties) under acidic conditions to reveal polar OH groups. The extraction coefficients of the porphyrazines between 2-octanol and phosphate buffered saline solution were measured. Comparison of the partition coefficients of the carbohydrate-substituted porphyrazines and their deprotected counterparts revealed that structural alteration offers a way to significantly increase the hydrophilicity of substituted porphyrazines.